EP0156136B1 - High pressure sealing - Google Patents

Abstract

A seal assembly for sealing two relatively movable parts against fluid leakage comprises a seal ring of compressible material mounted on one of the parts, and a supporting ring of non-compressible material positioned in an axial annular groove in said seal ring, said groove being open towards the annular gap to be sealed and surrounded by an annular web, said supporting ring being arranged to be radially displaceable in that groove with limited elastic deformation of said annular web.

Description

The invention relates to a high-pressure seal for an axially displaceable and / or rotatable piston, a piston rod or shaft, with at least one sealing or guide ring made of elastically or plastically deformable material and a support ring which bears against it and which essentially does not exist under the operating conditions deforming hard material.

Known high-pressure seals of this type (DE-B-2 227 042) have a rigidly mounted support ring made of material which is practically non-deformable under operating conditions and which has a seal made of materials which are elastically or plastically deformable under pressure, such as elastomers, PTFE-impregnated plastic or mineral fiber fabrics and / or compounds or the like in the form of a grooved ring, a roof collar, a square cord, a scraper ring or other supports and chambers. A guide ring provided simultaneously with or instead of the seal made of the materials deformable under pressure serves to support the seal and / or to guide plungers, piston rods, pistons or shafts and the like and must also be supported and chambered. The support ring is therefore provided rigidly mounted on the side of the seal facing away from the pressure. An annular gap remains between the parts moving relative to one another. If this is chosen so large that the parts run against each other and the resulting destruction of the sliding surfaces is avoided, the deformable seal or the guide ring is extruded into the annular gap under the operating pressure and, depending on the operating conditions, the seal is destroyed faster or slower. If, on the other hand, the annular gap is chosen to be so small that it is not possible to extrude the deformable seal or the guide ring into the annular gap, the inevitable radial path deviations lead to the tarnishing of the parts which are moved relative to one another and to one another and to the destruction of the sliding surfaces.

The object of the invention is now to provide an inexpensive high-pressure seal of the type mentioned, which has an extended wear-free life.

To achieve this object, the device of the type mentioned is equipped according to the invention with the features specified in the characterizing part of claim 1.

According to the invention, the support ring is mounted in an annular groove of the sealing or guide ring and can be displaced radially elastically under its limited deformation. The annular gap between the support ring and the part moving relative to it can be chosen so small that extrusion of the sealing or guide ring into the annular gap is excluded. On the other hand, the sliding surfaces of the support ring and piston, piston rod or shaft cannot be destroyed by lateral running, since the support ring is not rigidly mounted and can move radially. With suitable material combinations of sealing or guide ring, support ring surface and surface of the part moved relative to this, slight concentric radial deformation of the support ring under high pressure results in calibration of the support ring during operation by means of the interacting sliding surface, so that the annular gap practically disappears .

The support ring can be carried out with a slight radial play relative to the ring web of the sealing or guide ring, so that misalignments caused by production and installation between the support ring and piston, piston rod or shaft are compensated for before the support ring is enclosed by the ring web of the sealing or guide ring under operating pressure .

The invention further relates to a sealing or guide ring made of deformable material under pressure for a high-pressure seal according to claim 1 with the features mentioned in claim 5.

In the following preferred embodiments of the high pressure seal are further explained with reference to the attached drawings.

• Fig. 1 eine längsgeschnittene Hochdruckdichtung für einen Plungerkolben;
• Fig. 1a und 1b Vergrößerungen des in Fig. 1 eingekreisten Bereichs;
• Fig. 2 eine längsgeschnittene abgewandelte Hochdruckdichtung für einen Plungerkolben;
• Fig. 3 eine längsgeschnittene Hochdruckdichtung für einen Kolben
• Fig. 3a und 3b Vergrößerungen des in Fig. 3 eingekreisten Bereichs und
• Fig. 4 eine längsgeschnittene abgewandelte Hochdruckdichtung für einen Kolben.

Show it:

• Figure 1 is a longitudinally cut high pressure seal for a plunger.
• 1a and 1b enlargements of the area encircled in Fig. 1;
• Figure 2 is a longitudinally cut modified high pressure seal for a plunger.
• Fig. 3 is a longitudinally cut high pressure seal for a piston
• 3a and 3b enlargements of the area encircled in FIG. 3 and
• Fig. 4 is a longitudinally cut modified high pressure seal for a piston.

The high-pressure seal for a plunger 6 shown in axial section in FIGS. 1, 1a and 1b comprises a guide ring 2 which, at its end cooperating with the support ring 1, has an annular groove 2a with an essentially radial annular step surface 2b, which is open towards this and towards the annular gap 3 to be sealed and has an axially projecting annular web 2c delimiting it on the side facing away from the annular gap 5.

The guide ring 2 consists of filled PTFE. The support ring 1 lies in the annular groove 2a Sintered metal (DEVA metal) against their ring step surface 2b. Its circumferential surface 1 facing the annular gap 3 is somewhat recessed relative to the circumferential surface 2d of the guide ring 2, which is more distant from the annular web 2c, with a coaxial alignment.

The circumferential surface 2b 'of the ring web 2c facing the annular gap 3 corresponds in diameter to the circumferential surface 1b of the support ring 1 (FIG. 1a) facing away from the annular gap 3, but it can also be larger by a predetermined small distance before installation (radial clearance 4 in FIG. 1b), but then rests against them in the operating state with elastic and / or plastic deformation. The support ring 1 is mounted so as to be radially elastically displaceable with limited deformation of the ring web 2c.

The guide ring 2 has in its axial end face facing away from the annular groove 2a an essentially V-shaped groove in cross section for receiving a roof collar seal 7.

The high-pressure seal constructed in this way is received in a plunger bushing 5 and seals against the plunger 6 which can be displaced therein. A pressure ring 18 surrounding the plunger 6 is urged by a spring device 17 in the direction of the high-pressure seal and presses it against a seat 23 of the plunger bushing 5 which protrudes radially inwards and which protrudes radially towards the plunger 6 to such an extent that the pressure-facing side surface of the support ring 1 on it z. T. is present. Between the seat 23 and the plunger 6 there is an annular maintenance chamber 8 which is provided with a feed channel 12 and a discharge channel 13 in the form of radial bores for lubricating and / or cooling the plunger 6. On the side of the seat 23 facing away from the pressure, a second high-pressure seal is provided, which comprises a maintenance chamber seal 9 formed from roof seals, a guide ring 14 and a support ring 15 and is preloaded against the seat 23 by a holding element 16 which can be fixed in the plunger bushing 5. Guide ring 14 or support ring 15 correspond to the guide ring 2 or support ring 1 already described, both high-pressure seals point in the same direction.

The plunger 6 is connected via a coupling 10 to the crosshead of a conventional crank drive (not shown) and in one through the high pressure seal. closed delivery chamber 11 reciprocally displaceable. During the delivery stroke (movement to the left in FIG. 1), the plunger 6 generates a delivery pressure in the delivery chamber 11, which is indicated by the arrow P. Under the effect of this pressure, the high-pressure seal pressed against the seat 23 by the spring device 17 and the pressure ring 18 is further compressed. The cross-sectionally V-shaped groove of the guide ring 2 prevents excessive deformation of the roof boot seal 7. The guide ring 2 cannot be extruded even under high pressure through the very small annular gap 3 between the support ring 1 and the plunger 6 and presses the support ring 1 against the Seat 23 of the plunger bushing 5. This pressing prevents the guide ring 2 from being extruded between the support ring 1 and the seat 23; due to the resulting radially inward pressure of the guide ring 2 on the outer circumference of the support ring 1, this is at most minimally radially compressed. However, there is no start-up damage to the surface of the plunger 6 or the inner circumferential surface of the support ring 1, since the support ring 1 can deflect radially while deforming the guide ring 2 and the permissible surface pressure values are not exceeded even when the sliding surfaces are touched.

A modified high-pressure seal for a plunger 6 is shown in FIG. 2, parts corresponding to FIGS. 1, 1a and 1b not being described and some of which are not shown in the figure. In this modified high-pressure seal, a support ring 1, which is essentially the same as that already described, is mounted radially displaceably in a seal ring 19 in the manner also described above. The sealing ring 19 has on its axial end face facing away from the annular groove receiving the support ring 1, radial sealing lips which, in relation to the plunger bushing wall or the plunger 6, develop a sealing effect corresponding to the roof seal seal already described. In this embodiment, sealing ring 19 and support ring 1 are not pressed directly against the seat of the plunger bushing, but instead against a rigid retaining ring 21 made of material which is not deformable under operating conditions and which has such a large radial clearance with respect to the plunger 6 that it does not start on the retaining ring 21 can. A guide ring 20 made of elastically and / or plastically deformable material is inserted in the inner circumferential surface of the retaining ring 21 to guide the plunger 6. Since a high-pressure seal comprising the sealing ring 19 and the support ring 1 is arranged on the pressure side of the guide ring 20, it does not have to be secured against deformation under pressure, as in the embodiment described with reference to FIG. 1. On the side of the seat facing away from the pressure, again analogous to the arrangement in FIG. 1, a sealing ring 22 with radial sealing lips and a supporting ring supporting it are provided, which are prestressed by a holding element against a holding ring supported on the seat with a guide ring embedded in its inner peripheral surface.

While the exemplary embodiments described so far relate to high-pressure seals which sealingly enclose a part which is movable in them, the high-pressure seal being arranged on a housing part which is not itself moving, it can instead also be arranged on the moving part itself, as is the case below with reference to FIG. 3 and 4 show the exemplary embodiments described.

3 shows a piston 100 which is reciprocally displaceable in a cylinder 105 by a piston rod 106 and which is sealed against the inner wall of the cylinder 105, along which it slides, by a high-pressure seal according to the invention. The high-pressure seal comprises a support ring 101 which is arranged in an annular groove 102a (cf. FIG. 3a) of a piston guide ring 102. The annular groove 102a is open toward the end of the piston guide ring 102 which cooperates with the support ring 101 and towards the annular gap 103 to be sealed and has an essentially radial annular step surface 102b and an axially projecting annular web 102c delimiting it on the side facing away from the annular gap 103. As in the embodiments described above, the circumferential surface 101a of the support ring 101 facing the annular gap 103 also recedes somewhat in relation to the circumferential surface 102d of the guide ring 102 distant from the ring web 102c in the case of coaxial alignment. As shown in FIGS. 3a and 3b, the circumferential surface 102b 'of the ring web 102c facing the annular gap 103 corresponds in diameter to the circumferential surface 101b of the support ring 101 facing away from the annular gap 103 or is a predetermined small distance, namely around the radial clearance 104, before it is installed. larger, but is in any case in the operating state, possibly with elastic and / or plastic deformation against the peripheral surface 101b of the support ring. In this embodiment too, the support ring 101, which rests in the annular groove 102a against its annular step surface 102b, 102b ', is mounted so as to be radially elastically displaceable with limited deformation of the annular web 102c. The materials used for the piston guide ring 102 and the support ring 101 correspond to the materials already specified in the aforementioned embodiments.

In its axial end face facing away from the ring groove 102a, the piston guide ring 102 has a groove which is essentially V-shaped in cross section for receiving a roof boot seal 107.

The piston 100 comprises two piston segments 108, 109 arranged on the end section of the piston rod 106, which are fixed to the piston rod 106 by a fastening element 113 and thereby fix an intermediate ring 112 between them in a clamped fit. The outer diameter of the piston segments 108, 109 and the intermediate ring 112 are dimensioned so much smaller than the inner diameter of the cylinder 105 that the piston segments 108, 109 and the intermediate ring 112 do not match the inner surface of the cylinder 105 in operation even with the small radial deflections of the piston during operation Can come into contact.

A high-pressure seal is arranged between each piston segment 108 or 109 and the intermediate ring 112 such that the support ring 101 bears against the intermediate ring 112 and the high-pressure seals when the fastening element 113 is tightened by moving the piston segments 108, 109 towards one another from opposite sides against the intermediate ring 112 pressed and slightly compressed and preloaded. The high-pressure seals point in opposite directions.

The piston rod 106 is either coupled to a crosshead of a conventional crank drive via a coupling 110 or is used for axial power transmission. In the first case, the reciprocal movement of the piston 100 and the corresponding change in volume of the cylinder chambers 111 and 123, respectively, result in a pressure P on the z. B. generated liquids to be conveyed; in the second case z. B. by introducing a hydraulic medium into the cylinder chambers 111 and 123, a pressure is exerted on the piston 100, which is transmitted by means of the piston rod 106 to a device to be actuated.

Under the operating pressure in the cylinder chambers 111 and 123, which acts on the piston guide ring 102 and the support ring 101 via the roof boot seal 107, the piston guide ring 102 deforms and embeds the support ring 101 in a radially displaceable manner. Extrusion of the piston guide ring 102 into the space between the inner wall of the cylinder 105 and the intermediate ring 112 is excluded because of the strong pressure of the support ring 101 against it and because of the minimal annular gap 103. Manufacturing and installation-related misalignments between the inner wall of the cylinder 105 and the support ring 101 are compensated for by radial displacement of the support ring 101, which is particularly facilitated if, as in FIG. 3b, a radial play 104 between the ring web 102c of the piston guide ring 102 and the support ring 101 is provided.

FIG. 4 shows a modified high-pressure seal of the type already described with reference to FIG. 3, in which a deformable piston guide ring 120 is embedded in the outer peripheral surface of the intermediate ring. Analogous to the embodiment in FIG. 3, sealing rings 119 and support rings 101 arranged in their annular groove are provided between the piston segments. The sealing rings 119 have radial sealing lips that function as the roof boot seals 107 in FIG. 3 fulfill. Since the operating pressure P does not occur in the space enclosed by the intermediate ring, the inner wall of the cylinder and the support rings 101, the piston guide ring 120 need not have any special support, but can simply be embedded in the outer circumferential surface of the intermediate ring. The functions of the piston in FIG. 4 otherwise correspond entirely to those of the piston 100 in FIG. 3.

Comparative tests were carried out with a plunger pump similar to the type described with reference to FIG. 1, in which a high-pressure seal of the known type mentioned at the beginning and a high-pressure seal according to the invention were used.

In both tests, the roof boot seal consisted of four PTFE-impregnated asbestos fabric sleeves, the plunger piston had a running surface with a chrome carbide layer MK22 applied by means of the melting process. For the high-pressure seal of the known type, a rigidly mounted support ring made of AB 4 S bronze was used, in which a band made of filled PTFE (compound no. 10 from Busak & Luyken) was embedded as a guide ring. A support ring made of sintered metal with emergency running properties (DEVA metal) was used for the high-pressure seal according to the invention; the guide ring consisted, as in the known seal, of filled PTFE (compound No. 10 from Busak & Luyken).

The running time to leakage was approximately 50 hours in the known high-pressure seal. The leak was due to the support ring worn by radially tarnished pistons and the collapsed roof seals.

The high-pressure seal according to the invention still ran after 240 hours with flawless roof seals and undamaged guide ring; the experiment was stopped after this period.

After 240 hours, the support ring showed slight traces of spotting evenly distributed over the entire inner circumferential surface, which are probably due to the fact that the support ring was radially compressed during the pressure stroke and calibrated by the harder plunger surface. This assumption is supported by the fact that the inner diameter of the support ring has been increased by approximately 0.01 mm.

In addition to the advantageous combination of a support ring made of metal with emergency running properties and a plunger with a much harder surface, it is of course also possible to manufacture the support ring from materials that are as hard as or harder than the plunger surface or at least the inner circumferential surface has a correspondingly hard layer.

Claims (5)

1. A high-pressure seal for an axially-sliding and/or rotating piston, piston-rod or shaft, with at least one sealing or guiding ring of a material which is elastically or plastically deformable under pressure and, resting against this, a support-ring of a hard material which is substantially undeformable under the operating conditions encountered, characterised in that:

a) the sealing or guiding ring (2, 14, 19, 102, 119), at its end where it rests against the support-ring (1, 101), has an annular groove (2a, 102a), which is open towards the support-ring (1, 101) and towards the annular gap (3, 103) which is to be sealed, the annular groove (2a, 102a) having a substantially radial surface (2b, 102b) and an annular step (2c, 102c) projecting axially at the side of the groove (2a, 102a) opposite the annular gap (3, 103), and in that:

b) the surface (1a, 101a) of the support-ring (1, 101) at the annular gap (3,103) is radially set back a little from the runnig surface (2d, 102d) of the sealing or guiding ring (2, 14, 19, 102, 119), these two surfaces nevertheless being parallel to each other, and in that:

c) the diameter of the annular surface (2b', 102b'), opposite the annular gap (3, 103) of the step (2c, 102c), is the same as the diameter of the neighbouring annular surface (1b, 101b) of the support-ring (1, 101), or is slightly greater before assembly of the seal but decreases during operation by elastic or plastic deformation so that these two surface rest in contact with each other, and in that:

d) the support-ring (1, 101), which rests in the annular groove (2a, 102a) in contact with the radial (2b, 102b) and axial (2b', 102b') surfaces of the groove (2a, 102a), is radially elastically shiftable by the limited deformation of the step (2c, 102c).

2. High-pressure seal as claimed in Claim 1, characterised in that the sealing or guiding ring (2 14, 102) has a groove, substantially V-shaped in cross section, in its end away from the annular groove (2a, 102a), for taking a V-section lip-seal (7, 107).

3. High-pressure seal as claimed in Claim 1, characterised in that the axial face of the sealing or guiduing ring (19, 119) away from the annular groove (2a, 102a) has at least one radial sealing lip.

4. High-pressure seal as claimed in Claims 1 to 3, characterised in that the supportring (1, 101) is made of metal and/or a ceramic oxide.

5. A sealing or guiding ring of a material which is deformable under pressure, for a high-pressure seal of the kind claimed in Claim 1, characterised in that the base ring has:

a) an annular groove (2a, 102a) which is open towards the annular gap (3, 103) which is to be sealed, the annular groove (2a, 102a) having a substantially radial surface (2b, 102b) and an annular step (2c, 102c) projecting axially at the side of the groove (2a, 102a) opposite the annular gap (3, 103), and in that:

b) the diameter of the annular surface (2b', 102b'), opposite the annular gap, of the step is the same as the diameter of the neighbouring annular surface of the supportring (1, 101), or is slightly greater.

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